textproduct: Rapid City

KEY MESSAGES

- Passing showers and storms still look likely overnight.

- Becoming windy on Monday, especially across the northwest.

- Fire weather concerns on Monday are the wildcard across the northwest.

UPDATE

Issued at 913 PM MDT Sun Sep 13 2026

A few showers and thunderstorms have drifted into the area from the southwest this evening. Any changes to the forecast have been centered around narrowing down the location of where rain and storms are most likely and when. So far, no reports of severe weather, just some gusts upwards of 45 to 50 mph. These storms will continue to develop just west of the area and drift into NE WY and W SD through the overnight. Severe weather is not expected from these storms but gusty winds, small hail, lightning, and brief heavy rainfall can't be ruled out.

A frontal passage is still expected tomorrow so expect winds to swing to the west as the front tracks through your area. Wind gusts are likely to be strong with the strongest winds in NW SD. Maintained the Wind Advisory that was inherited.

DISCUSSION

(This Evening Through Sunday) Issued at 1232 PM MDT Sun Sep 13 2026

Latest water vapor imagery shows 500hpa low spinning across southern WA state with ridging setting up from eastern MT into eastern CO. Upper flow across the Dakotas has turned more northwesterly with broad cyclonic flow setting up across the Great Lakes into New England. Broad high pressure still remains in control across the southern tier of states. At the surface, low pressure is setting up across southern WY. Southeast surface winds ahead of this low are advecting in a lower cloud deck out of NE into much of the forecast area. Temperatures at 18Z are in the low to mid 60s.

The forecast through the next 24 hours presents some interesting challenges. First in a series of shortwaves ejects into the FA this evening, with strengthening 700hpa theta-e forcing and moisture advection, as seen with increasing 850hpa dewpoints. This should lead to increasing coverage of rainfall across the forecast area beginning later this evening and continuing through the night. Can't rule out some elevated convection. Hi-res models are showing the potential for some of these storms to mix down the strong 700hpa and 850hpa winds as well. The rain will be welcome for sure. On Monday, the rain will push east of the FA during the morning hours. The cold front sweeps through with gusty NW winds found on the backside along with modest CAA. By 18Z Monday models are showing from 4 to 5 mb/3hrly pressure rises on backside of front. It appears that winds will become nearly linked during the afternoon hours, so have opted to hoist a wind advisory for parts of our northern FA during the day Monday. This also leads to a tricky fire weather concern. Parts of our NW are at critical fire danger levels. The unknown is how much rain they may receive overnight, helping to put a small damper on those critical levels. Additionally, there might only be a narrow window when RH values and winds meet up for fire weather headlines. For now, am going to forego any fire weather headlines and let later shifts evaluate. Also, given CAA and anticipated cloud cover, lowered high temperatures on Monday.

After Monday, the rest of the week still appears to be seasonable temperature wise. Precipitation chances move back into the area beginning late Tuesday night and generally continue through the rest of the week.

AVIATION

(For the 12Z TAFS Through 12Z Tuesday Morning) Issued At 525 AM MDT Mon Sep 14 2026

Showers and storms will continue to develop and move across western SD this morning. This precip along with low stratus has created widespread MVFR/IFR conditions across western SD. Precip should move out of the area by ~18z with conditions improving to VFR from west to east through the morning hours.

Winds will shift from the southeast to west-northwest as the morning progresses. Winds will remain strong with gusts of 25 to 35 KT over much of northeastern WY into the western SD plains. Northwestern SD will see stronger winds with gusts of 40 to 50KT. The strong winds will continue through the evening hours.

UNR WATCHES/WARNINGS/ADVISORIES

SD...Wind Advisory from 11 AM this morning to 9 PM MDT this evening for SDZ001-002-012>014-073-078. WY...None.